The present invention relates to an optical device that is transmissive.
There has been a desire for improved optical filters whose spectral characteristics can be customised, which are stable and feasible to fabricate, and which are compact. There are real-world applications for such optical devices in at least the visible and infrared parts of the spectrum.
In some fields it is desirable to be able to change the transmission properties in use, such as for see-through displays, security applications or for light and/or heat control.
The present invention has been devised in view of the above problems.
Accordingly, the present invention provides a transmissive optical device comprising:
a layer of light absorber material in the solid state;
a partially-reflective layer, and
a spacer layer between the layer of light absorber material and the partially-reflective layer.
Further optional aspects are defined in the dependent claims.
Throughout this specification, the terms ‘optical’ and ‘light’ are used, because they are the usual terms in the art relating to electromagnetic radiation, but it is understood that in the context of the present specification they are not limited to visible light. It is envisaged that the invention can also be used with wavelengths outside the visible spectrum, such as infrared and ultraviolet light.